One of the biggest challenges faced by modern society is to secure sustainable resources that meet burgeoning energy demands (R. Marom et al., Journal of Materials Chemistry 21, 9938 (2011)). One area of great interest is developing lithium (Li) batteries suitable for large-scale applications, such as transportation and energy storage (J. Tarascon and M. Armand, Nature 414, 359 (November 2001)). Currently, Li-ion batteries are used in electric vehicles (EVs), but factors including cost and longevity limit their prevalence (O. Egbue and S. Long, Energy Policy 48, 717 (2012)). Safety is also a primary concern; most commercial Li-ion batteries consist of a flammable mixture of alkyl carbonates that serves as the electrolyte solvent.
In the last decade, there has been extensive efforts to introduce alternative solvents, salts, and additives that can improve the quality and performance of electrolytes (D. Aurbach et al., Electrochimica Acta 50, 247 (2004)). The preparation of polyelectrolytes is an emerging area of interest due to their potential lower costs, easy handling, and better safety. Poly(ethylene oxide) (PEO) is the most prominently featured homopolymer in this field due its unique ability to solvate Li-based salts. The crystallinity of PEO, however, hinders ionic conductivity, rendering PEO-LiX electrolytes useful at temperatures between 60° to 80° C. (F. Croce et al., Nature 394, 456 (1998)). Dendrite formation at the anode electrode remains a persistant issue, causing shortcircuits and overcharging, which can lead to cell ignition or explosion (S. Tobishima et al., Journal of Power Sources 90, 188 (2000); H. Ghassemi et al., Applied Physics Letters 99, 123113 (2011)). Accordingly, there is a need for new electrolyte compositions for lithium ion batteries, and other types of alkali metal ion batteries.